News About Semiconductor Technologyhttp://www.spacedaily.com/Chip_Technology.html
News About Semiconductor TechnologyTue, 06 DEC 2016 03:28:27 AESTTue, 06 DEC 2016 03:28:27 AESTen-us
Sussex, UK (SPX) Dec 06, 2016 -
Scientists at the University of Sussex have invented a ground-breaking new method that puts the construction of large-scale quantum computers within reach of current technology.

Quantum computers could solve certain problems - that would take the fastest supercomputer millions of years to calculate - in just a few milliseconds. They have the potential to create new materials and medicines, as well as solve long-standing scientific and financial problems.

Universal quantum computers can be built in principle - but the technology challenges are tremendous. The engineering required to build one is considered more difficult than manned space travel to Mars - until now.

Quantum computing on a small scale using trapped ions (charged atoms) is carried out by aligning individual laser beams onto individual ions with each ion forming a quantum bit. However, a large-scale quantum computer would need billions of quantum bits, therefore requiring billions of precisely aligned lasers, one for each ion.

Instead, scientists at Sussex have invented a simple method where voltages are applied to a quantum computer microchip (without having to align laser beams) - to the same effect.

Professor Winfried Hensinger and his team also succeeded in demonstrating the core building block of this new method with an impressively low error rate at their quantum computing facility at Sussex.

Professor Hensinger said: "This development is a game changer for quantum computing making it accessible for industrial and government use. We will construct a large-scale quantum computer at Sussex making full use of this exciting new technology."

Quantum computers may revolutionise society in a similar way as the emergence of classical computers. Dr Seb Weidt, part of the Ion Quantum Technology Group said: "Developing this step-changing new technology has been a great adventure and it is absolutely amazing observing it actually work in the laboratory."

'Trapped-ion quantum logic with global radiation fields'

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Tue, 06 DEC 2016 03:28:27 AEST
Tokyo, Japan (SPX) Dec 06, 2016 -
In electronics, lower power consumption leads to operation cost savings, environmental benefits and the convenience advantages from longer running devices. While progress in energy efficiencies has been reported with alternative materials such as SiC and GaN, energy-savings in the standard inexpensive and widely used silicon devices are still keenly sought. K Tsutsui at Tokyo Institute of Technology and colleagues in Japan have now shown that by scaling down size parameters in all three dimensions their device they can achieve significant energy savings.

Tsutsui and colleagues studied silicon insulated gate bipolar transistors (IGBTs), a fast-operating switch that features in a number of every day appliances. While the efficiency of IGBTs is good, reducing the ON resistance, or the voltage from collector to emitter required for saturation (Vce(sat)), could help increase the energy efficiency of these devices further.

Previous investigations have highlighted that increases in the "injection enhancement (IE) effect", which give rise to more charge carriers, leads to a reduction in Vce(sat). Although this has been achieved by reducing the mesa width in the device structure, the mesa resistance was thereby increased as well. Reducing the mesa height could help counter the increased resistance but is prone to impeding the (IE) effect.

Instead the researchers reduced the mesa width, gate length, and the oxide thickness in the MOSFET to increase the IE effect and so reduce Vce(sat) from 1.70 to 1.26 V. With these alterations the researchers also used a reduced gate voltage, which has advantages for CMOS integration.

They conclude, "It was experimentally confirmed for the first time that significant Vce(sat) reduction can be achieved by scaling the IGBT both in the lateral and vertical dimensions with a decrease in the gate voltage."

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Tue, 06 DEC 2016 03:28:27 AEST
Surrey, UK (SPX) Nov 25, 2016 -
Has the time come to replace traditionally used silicon with printable organic semiconductor inks? University of Surrey scientists believe so, especially for future electronics that need to be flexible, lightweight, wearable and low-cost. Single crystal semiconductors, such as silicon, have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt at very high temperatures, in special chambers filled with inert gas, using time-consuming and energy intensive processes.

A new class of crystalline materials, called organic semiconductors, can also be grown as single crystals, but in a very different way, using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics, targeting numerous applications ranging from field effect transistors and light emitting diodes to medical x-ray detectors and miniature lasers.

New research, published in Nature Communications, conducted by a team of researchers from the University of Surrey and National Physical Laboratory, demonstrates for the first time a low-cost, scalable spray-printing process to fabricate high-quality isolated organic single crystals.

The method is suitable for a wide variety of semiconducting small molecules, which can be dissolved in solvents to make semiconducting inks, and then be deposited on virtually any substrate. The key aspect is in combining the advantages of antisolvent crystallization and solution shearing.

The crystals' size, shape and orientation are then controlled by the spay angle and distance to the substrate, which govern the spray droplets' impact onto the antisolvent's surface. These crystals are high quality structures, as confirmed by a combination of characterisation techniques, including polarised optical and scanning electron microscopy, x-ray diffraction, polarised Raman spectroscopy and field-effect transistor tests.

"This method is a powerful, new approach for manufacturing organic semiconductor single crystals and controlling their shape and dimensions," said Dr Maxim Shkunov from the Advanced Technology Institute at the University of Surrey.

"If we look at silicon, it takes almost 15000C to grow semiconductor grade crystals, while steel spoons will melt at this temperature, and it will fetch a very hefty electric bill for just 1 kg of silicon, same as for running a tea kettle for over 2 days non-stop. And then, you would need to cut and polish those silicon 'boules' into wafers.

"We can make single crystals in a much simpler way, entirely at room temperature with a Pounds 5 artist spray brush. With a new class of organic semiconductors based on carbon atoms, we can spray-coat organic inks onto anything, and get more or less the right size of crystals for our devices right away."

Dr Maxim Shkunov, lead author of the research, continued: "The trick is to cover the surface with a non-solvent so that semiconductor molecules float on top and self-assemble into highly ordered crystals.

"We can also beat silicon by using light emitting molecules to make lasers, for example, - something you can't do with traditional silicon. This molecular crystals growth method opens amazing capabilities for printable organic electronics."

Tue, 06 DEC 2016 03:28:27 AEST
Washington DC (SPX) Nov 25, 2016 -
In science, sometimes the best discoveries come when you're exploring something else entirely. That's the case with recent findings from the National Institute of Standards and Technology (NIST), where a research team has come up with a way to build safe, nontoxic gold wires onto flexible, thin plastic film. Their demonstration potentially clears the path for a host of wearable electronic devices that monitor our health.

The finding might overcome a basic issue confronting medical engineers: How to create electronics that are flexible enough to be worn comfortably on or even inside the human body - without exposing a person to harmful chemicals in the process - and will last long enough to be useful and convenient. "Overall this could be a major step in wearable sensor research," said NIST biomedical engineer Darwin Reyes-Hernandez.

Wearable health monitors are already commonplace; bracelet-style fitness trackers have escaped mere utility to become a full-on fashion trend. But the medical field has its eye on something more profound, known as personalized medicine. The long-term goal is to keep track of hundreds of real-time changes in our bodies - from fluctuations in the amount of potassium in sweat to the level of particular sugars or proteins in the bloodstream.

These changes manifest themselves a bit differently in each person, and some of them could mark the onset of disease in ways not yet apparent to a doctor's eye. Wearable electronics might help spot those problems early.

First, though, engineers need a way to build them so that they work dependably and safely - a tall order for the metals that make up their circuits and the flexible surfaces or "substrates" on which they are built.

Gold is a good option because it does not corrode, unlike most metals, and it has the added value of being nontoxic. But it's also brittle. If you bend it, it tends to crack, potentially breaking completely - meaning thin gold wires might stop conducting electricity after a few twists of the body.

"Gold has been used to make wires that run across plastic surfaces, but until now the plastic has needed to be fairly rigid," said Reyes-Hernandez. "You wouldn't want it attached to you; it would be uncomfortable."

Reyes-Hernandez doesn't work on wearable electronics. His field is microfluidics, the study of tiny quantities of liquid and their flow, typically through narrow, thin channels. One day he was exploring a commercially available porous polyester membrane - it feels like ordinary plastic wrap, only a lot lighter and thinner - to see if its tiny holes could make it useful for separating different fluid components. He patterned some gold electrodes onto the membrane to create a simple device that would help with separations.

While sitting at his desk, he twisted the plastic a few times and noticed the electrodes, which covered numerous pores as they crisscrossed the surface, still conducted electricity. This wasn't the case with nonporous membranes.

"Apparently the pores keep the gold from cracking as dramatically as usual," he said. "The cracks are so tiny that the gold still conducts well after bending."

Reyes-Hernandez said the porous membrane's electrodes show even higher conductivity than their counterparts on rigid surfaces, an unexpected benefit that he cannot explain as yet. The next steps, he said, will be to test changes in conductivity over the long term after many bends and twists, and also to build some sort of sensor out of the electrode-coated membrane to explore its real-world usability.

"This thin membrane could fit into very small places," he said, "and its flexibility and high conductivity make it a very special material, almost one of a kind."

Tue, 06 DEC 2016 03:28:27 AEST
Gothenburg, Sweden (SPX) Nov 18, 2016 -
What do fire flies, Huygens's wall clocks, and even the heart of choir singers, have in common? They can all synchronize their respective individual signals into one single unison tone or rhythm. Now researchers at University of Gothenburg have taught two different emerging classes of nano-scopic microwave signal oscillators, which can be used as future spintronic neurons, to sing in unison with their neighbours.

Earlier this year, they announced the first successful synchronization of five so-called nano-contact spin torque oscillators [1]. In that system, one of the nano-contacts played the role of the conductor, deciding which note to sing, and the other nano-contacts happily followed her lead.

This synchronized state was best described as driven and directional, since every nano-contact in the chain only listened to its upstream neighbor, adjusted its own frequency in accordance, and then enforced this frequency on the next neighbor downstream. The interaction strength is the same between each neighbor and the chain can hence be made very long without any oscillator singing out of tune.

This time around the same research group has demonstrated synchronization of as many as nine nano-constriction based spin Hall nano-oscillators. In this system, there is no conductor. Instead the organization is entirely flat with each oscillator now listening to both its neighbors.

As a consequence, the note is decided in a democratic manner, with the final unison state being an agreed on compromise between all the original individual frequencies. The synchronized state is hence best described as both mutual and bi-directional. This means that information can now travel in both directions and a perturbation at any location along the oscillator chain can lead to an adjustment of the tone of the entire choir.

By making use of the spin Hall effect, not only to power each oscillator but also to enhance the coupling between the nano-constrictions, the authors were also able to synchronize two oscillators separated by up to 4 micrometers.

"As the nano-constrictions are only 100 nm in size, this would correspond to a line of nine singers, each singer standing some 80 meters from its nearest neighbor, and still all singers staying in tune," says Ahmad Awad, the first author of the study. "The synchronization is hence very robust".

The researchers envision that both types of oscillators can play key parts in future oscillatory networks for wave based neuromorphic computing. For example, inputs and outputs from the network require directionality to make sure the information travels in the correct direction and that the outputs are unperturbed by any potential interference or other spurious signals.

However, inside the network, one wants to make use of the parallelism and the collective response of all oscillators. This hence requires bi-directionality and mutual synchronization within the network itself.

Says Prof. Johan Akerman, the principal investigator behind the results: "The demonstration of the key concepts of both driven and mutual synchronization in nano-scopic microwave oscillators is really only the first step.

"The robustness of our results now give us the design freedom to explore oscillator networks of any size using a wide range of different layouts only limited by one's imagination. Add the potential for neuromorphic computing and you can see why we are so excited!"

Tue, 06 DEC 2016 03:28:27 AEST
New Haven CT (SPX) Nov 18, 2016 -
If objects in motion are like rainwater flowing through a gutter and landing in a puddle, then quantum objects in motion are like rainwater that might end up in a bunch of puddles, all at once. Figuring out where quantum objects actually go has frustrated scientists for years.

Now a Yale-led group of researchers has derived a formula for understanding where quantum objects land when they are transmitted. It's a development that offers insight for controlling open quantum systems in a variety of situations.

"The formula we derive turns out to be very useful in operating a quantum computer," said Victor Albert, first author of a study published in the journal Physical Review X. "Our result says that, in principle, we can engineer 'rain gutters' and 'gates' in a system to manipulate quantum objects, either after they land or during their actual flow."

In this case, the gutters and gates represent the idea of dissipation, a process that is usually destructive to fragile quantum properties, but that can sometimes be engineered to control and protect those properties.

The principal investigator of the research is Liang Jiang, assistant professor of applied physics and physics at Yale.

It is a fundamental principle of nature that objects will move until they reach a state of minimal energy, or grounding. But in quantum systems, there can be multiple groundings because quantum systems can exist in multiple states at the same time - what is known as superposition.

That's where the gutters and gates come in. Jiang, Albert, and their colleagues used these mechanisms to formulate the probability of quantum objects landing in one spot or the other. The formula also showed there was one situation in which superposition can never be sustained: when a quantum "droplet" in superposition has landed in one "puddle" already, but hasn't yet arrived at the other "puddle."

"In other words, such a superposition state always loses some of its quantum properties as the 'droplet' flows completely into both puddles," Albert said. "This is in some ways a negative result, but it is a bit surprising that it always holds."

Both aspects of the formula will be helpful in building quantum computers, Albert noted. As the research community continues to develop technological platforms capable of supporting such systems, Albert said, it will need to know "what is and isn't possible."

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Tue, 06 DEC 2016 03:28:27 AEST
Okazaki, Japan (SPX) Nov 18, 2016 -
Kenji Ohmori (Institute for Molecular Science, National Institutes of Natural Sciences, Japan) has collaborated with Matthias Weidemuller (University of Heidelberg), Guido Pupillo (University of Strasbourg), Claudiu Genes (University of Innsbruck) and their coworkers to develop the world's fastest simulator that can simulate quantum mechanical dynamics of a large number of particles interacting with each other within one billionths of a second.

The dynamics of many electrons interacting with each other governs a variety of important physical and chemical phenomena such as superconductivity, magnetism, and chemical reactions. An ensemble of many particles thus interacting with each other is referred to as a "strongly correlated system".

Understanding the properties of strongly correlated systems is thus one of the central goals of modern sciences. It is extremely difficult, however, to predict theoretically the properties of a strongly correlated system even if one uses the post-K supercomputer, which is one of the world's fastest supercomputers planned to be completed by the year 2020 in a national project of Japan.

For example, the post-K cannot exactly calculate even the energy, which is the most basic property of matter, when the number of particles in the system is more than 30.

Instead of calculating with a classical computer such as the post-K, an alternative concept has been proposed and referred to as a "quantum simulator", in which quantum mechanical particles such as atoms are assembled into an artificial strongly correlated system whose properties are known and controllable.

The latter is then used to simulate and understand the properties of a different strongly correlated system, whose properties are not known. Huge investment to the development of quantum simulators has therefore been started recently in national projects of various countries including US, EU, and China.

The team has developed a completely new quantum simulator that can simulate the dynamics of a strongly correlated system of more than 40 atoms within one billionths of a second. This has been realized by introducing a novel approach in which an ultrashort laser pulse whose pulse-width is only 100 billionths of a second is employed to control a high-density ensemble of atoms cooled down to temperatures close to absolute zero.

Furthermore they have succeeded in simulating the motion of electrons of this strongly correlated system that is modulated by changing the strength of interactions among many atoms in the ensemble.

This "ultrafast quantum simulator" is expected to serve as a basic tool to investigate the origin of physical properties of matter including magnetism and, possibly, superconductivity.

This result will be published in Nature Communications, an online scientific journal of UK, on 16th November 2016.

For the first time, an international team of scientists led by a researcher at the University of California, Riverside has modified the energy spectrum of acoustic phonons - elemental excitations, also referred to as quasi-particles, that spread heat through crystalline materials like a wave - by confining them to nanometer-scale semiconductor structures. The results have important implications in the thermal management of electronic devices.

Led by Alexander Balandin, Distinguished Professor of Electrical and Computing Engineering and UC Presidential Chair Professor in UCR's Bourns College of Engineering, the research is described in a paper published Thursday, Nov. 10, in the journal Nature Communications. The paper is titled "Direct observation of confined acoustic phonon polarization branches in free-standing nanowires."

The team used semiconductor nanowires from Gallium Arsenide (GaAs), synthesized by researchers in Finland, and an imaging technique called Brillouin-Mandelstam light scattering spectroscopy (BMS) to study the movement of phonons through the crystalline nanostructures.

By changing the size and the shape of the GaAs nanostructures, the researchers were able to alter the energy spectrum, or dispersion, of acoustic phonons. The BMS instrument used for this study was built at UCR's Phonon Optimized Engineered Materials (POEM) Center, which is directed by Balandin.

Controlling phonon dispersion is crucial for improving heat removal from nanoscale electronic devices, which has become the major roadblock in allowing engineers to continue to reduce their size.

It can also be used to improve the efficiency of thermoelectric energy generation, Balandin said. In that case, decreasing thermal conductivity by phonons is beneficial for thermoelectric devices that generate energy by applying a temperature gradient to semiconductors.

"For years, the only envisioned method of changing the thermal conductivity of nanostructures was via acoustic phonon scattering with nanostructure boundaries and interfaces. We demonstrated experimentally that by spatially confining acoustic phonons in nanowires one can change their velocity, and the way they interact with electrons, magnons, and how they carry heat. Our work creates new opportunities for tuning thermal and electronic properties of semiconductor materials," Balandin said.

Tue, 06 DEC 2016 03:28:27 AEST
Seoul, South Korea (SPX) Nov 14, 2016 -
The Center for Integrated Nanostructure Physics, within the Institute for Basic Science (IBS) has developed the world's thinnest photodetector, that is a device that converts light into an electric current. With a thickness of just 1.3 nanometers - 10 times smaller than the current standard silicon diodes - this device could be used in the Internet of Things, smart devices, wearable electronics and photoelectronics. This 2D technology, published on Nature Communications, uses molybdenum disulfide (MoS2) sandwiched in graphene.

Graphene is a fantastic material: It's conductive, thin (just one-atom thick), transparent and flexible. However, since it does not behave as a semiconductor, its application in the electronics industry is limited. Therefore, in order to increase graphene's usability, IBS scientists sandwiched a layer of the 2D semiconductor MoS2 between two graphene sheets and put it over a silicon base. They initially thought the resulting device was too thin to generate an electric current but, unexpectedly, it did.

"A device with one-layer of MoS2 is too thin to generate a conventional p-n junction, where positive (p) charges and negative (n) charges are separated and can create an internal electric field. However, when we shine light on it, we observed high photocurrent. It was surprising! Since it cannot be a classical p-n junction, we thought to investigate it further," explains YU Woo Jong, first author of this study.

To understand what they found, the researchers compared devices with one and seven layers of MoS2 and tested how well they behave as a photodetector, that is, how they are able to convert light into an electric current. They found that the device with one-layer MoS2 absorbs less light than the device with seven layers, but it has higher photoresponsitivity.

"Usually the photocurrent is proportional to the photoabsorbance, that is, if the device absorbs more light, it should generate more electricity, but in this case, even if the one-layer MoS2 device has smaller absorbance than the seven-layer MoS2, it produces seven times more photocurrent," describes Yu.

Why is the thinner device working better than the thicker one? The research team proposed a mechanism to explain why this is the case. They recognized that the photocurrent generation could not be explained with classical electromagnetism, but could be with quantum physics. When light hits the device, some electrons from the MoS2 layer jump into an excited state and their flow through the device produces an electric current. However in order to pass the boundary between MoS2 and graphene, the electrons need to overcome an energy barrier (via quantum tunnelling), and this is where the one-layer MoS2 device has an advantage over the thicker one.

The monolayer is thinner and therefore more sensitive to the surrounding environment: The bottom SiO2 layer increases the energy barrier, while the air on top reduces it, thus electrons in the monolayer device have a higher probability to tunnel from the MoS2 layer to the top graphene (GrT).

The energy barrier at the GrT/MoS2 junction is lower than the one at the GrB/MoS2, so the excited electrons transfer preferentially to the GrT layer and create an electric current. Conversely, in the multi-layer MoS2 device, the energy barriers between GrT/MoS2 and GrB/MoS2 are symmetric, therefore the electrons have the same probability to go either side and thus reduce the generated current.

Imagine a group of people in a valley surrounded by two mountains. The group wants to get to the other side of the mountains, but without making too much effort. In one case ( the seven-layers MoS2 device), both mountains have the same height so whichever mountain is crossed, the effort will be the same. Therefore half the group crosses one mountain and the other half the second mountain.

In the second case (analogue to the one-layer MoS2 device), one mountain is taller than the other, so the majority of the group decide to cross the smaller mountain. However, because we are considering quantum physics instead of classical electromagnetism, they do not need to climb the mountain until they reach the top (as they would need to do with classical physics), but they can pass through a tunnel.

Although electron tunneling and walking a tunnel in a mountain are very different of course, the idea is that electric current is generated by the flow of electrons, and the thinner device can generate more current because more electrons flow towards the same direction.

Actually, when light is absorbed by the device and MoS2 electrons jump into an excited state, they leave the so-called holes behind. Holes behave like positive mobile charges and are essentially positions left empty by electrons that absorbed enough energy to jump to a higher energy status. Another problem of the thicker device is that electrons and holes move too slowly through the junctions between graphene and MoS2, leading to their undesired recombination within the MoS2 layer.

For these reasons, up to 65% of photons absorbed by the thinner device are used to generate a current. Instead, the same measurement (quantum efficiency) is only 7% for the seven-layer MoS2 apparatus.

"This device is transparent, flexible and requires less power than the current 3D silicon semiconductors. If future research is successful, it will accelerate the development of 2D photoelectric devices," explains the professor.

The creation of a qubit in zinc selenide, a well-known semi-conductor material, made it possible to produce an interface between quantum physics that governs the behaviour of matter on a nanometre scale and the transfer of information at the speed of light, thereby paving the way to producing quantum communications networks.

In today's computers, classical physics rules.

Billions of electrons work together to make up an information bit: 0, electrons are absent and 1, electrons are present. In quantum physics, single electrons are instead preferred since they express an amazing attribute: the electron can take the value of 0, 1 or any superposition of these two states. This is the qubit, the quantum equivalent of the classical bit. Qubits provide stunning possibilities for researchers.

An electron revolves around itself, somewhat like a spinning top. That's the spin. By applying a magnetic field, this spin points up, down, or simultaneously points both up and down to form a qubit.

Better still, instead of using an electron, we can use the absence of an electron; this is what physicists call a "hole." Like its electron cousin, the hole has a spin from which a qubit can be formed. Qubits are intrinsically fragile quantum creature, they therefore need a special environment.

Zinc selenide, or ZnSe, is a crystal in which atoms are precisely organized. It is also a semi-conductor into which it is easy to intentionally introduce tellurium impurities, a close relative of selenium in the periodic table, on which holes are trapped, rather like air bubbles in a glass.

This environment protects the hole's spin - our qubit - and helps maintaining its quantum information accurately for longer periods; it's the coherence time, the time that physicists the world over are trying to extend by all possible means. The choice of zinc selenide is purposeful, since it may provide the quietest environment of all semiconductor materials.

Philippe St-Jean, a doctoral student on Professor Sebastien Francoeur's team, uses photons generated by a laser to initialize the hole and record quantum information on it. To read it, he excites the hole again with a laser and then collects the emitted photons.

The result is a quantum transfer of information between the stationary qubit, encoded in the spin of the hole held captive in the crystal, and the flying qubit - the photon, which of course travels at the speed of light.

This new technique shows that it is possible to create a qubit faster than with all the methods that have been used until now. Indeed, a mere hundred or so picoseconds, or less than a billionth of a second, are sufficient to go from a flying qubit to a static qubit, and vice-versa.

Although this accomplishment bodes well, there remains a lot of work to do before a quantum network can be used to conduct unconditionally secure banking transactions or build a quantum computer able to perform the most complex calculations. That is the daunting task which Sebastien Francoeur's research team will continue to tackle.